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目的许多心血管变量存在着近日节律,心肌收缩反应及收缩蛋白基因表达是否存在着相应的周期性改变是值得深入研究.方法在24h内采用直接在大白鼠左心室内插入左心导管记录左室压(LVP)和左室压力微分最大值(dp/dtmax)以及检测比较心肌细胞的α-MHC基因表达改变.结果 LVP(P<0.001)、dp/dtmax(P<0.001)和α-MHC(P<0.01)的变化存在着近日节律.通过比较三者近日节律振幅显示LVP的振幅最大,dp/dtmax次之,α-MHC基因表达的节律振幅再次之,表明心肌收缩力的近日节律的变化是由心肌细胞内在和外在作用的结果.结论α-MHC基因表达水平的近日变化是决定着心肌收缩功能的近日节律的因素之一.“,”Objective A number of cardiovascular variables exhibit a circ adian rhythm. Whethe r myocardial contractile response and gene expression of the contractile protein also show changes with a similar period was here investigated. Method Circadi an variabilities in the left ventricular developed pressure (LVP) and contractil ity (LV dp/dt max) were measured in 24 Sprague-Dawley r ats by directly left ve ntricular catheterizing and compared with changes in the gene expression of α- myosin heavy chain (α-MHC) in myocytes obtained from the same animals by dot b lottin g analysis. Results A circadian rhythm was seen in the variabili ty of LVP (P<0.001), LV dp/dt max (P<0.001) and the bio chemically measured expression of the α- MHC gene (P<0.01). As compared to the amplitude of the rhythm i n α-MHC gene exp ression, the amplitude of the contractility rhythm was large (P< 0.01) and the ci rcadian amplitude of the LVP(P<0.001) was the largest, represent ing perhaps a co mposite of intracardiac plus any extracardiac contributions. Conclusion One of factors determing the circadian rhythm of myocardial contractile function is α -MHC gene expression level.